The moment Microsoft announced it would lock other browsers out of being installed on Windows RT, we all knew regulatory bodies the world over were wringing their hands. Today, this has been confirmed: in the wake of an investigation into Microsoft not complying with the existing antitrust rulings regarding browser choice, the EU has also announced it's investigating Windows 8 x86 and Windows 8 RT (ARM).

There are two issues that people gloss over on this subject. First, iOS and Windows RT are not in the same class. iOS is completely different from OS X. Windows RT, however, is the same basically as Windows 8. They use the same kernel and are designed the same way. Therefore, restrictions on Windows RT will have affects on Windows 8 and vice versa. Hence the investigation into browser lock in.

Whether the code is built from the same sources is irrelevant. It's about the market that the products compete in. Microsoft has no monopoly power in the ARM market; hence, the EU is blowing smoke here.

Secondly, Apple only sells iOS and OS X on their own hardware. If Microsoft only sold its own hardware, they would be able to do a lot more than they can now without getting in trouble. But the fact that they are basically pressuring OEM's into supporting Microsoft or going out of business will keep getting them sued.

Define pressure. I don't think you really know what you're talking about. The DOJ has been monitoring MS's behavior with OEMs for over a decade, and there is no pressure anymore.